Cathrea, the 17-year-old Livermore player who was the low amateur in the U.S. Women’s Open, won the par-4 18th with a bogey to extend the match, and finished off the 17-year-old Australian on the par-4 first.

Cathrea’s hands trembled as she stood over her 4-foot bogey putt on 18.

“I was like, ‘OK, calm down,'” said Cathrea, who will attend Oklahoma State. “Then my caddie was like ‘It’s just a 4-foot putt.’ And so I make it, and my hands are still shaking and I’m like, ‘Breathe, relax, you’ve got another hole.'”

Cathrea, a 3-and-1, second-round winner over Jennifer Kupcho of Westminster, Colo., in the morning, will face Bethany Wu of Diamond Bar, Calif., on Friday morning.

“Now I feel like I’m ready to play and I’m going to come out in the morning and play my best,” Cathrea said.